Horner Syndrome : Symptoms, Causes, Diagnosis and Management

Horner Syndrome : Symptoms, Causes, Diagnosis and Management

Horner syndrome (oculosympathetic palsy) is characterised by the classical triad of miosis (small and constricted pupil), partial ptosis (drooping of upper eyelid) and anhidrosis (loss of hemi facial sweating) caused due to disruption of sympathetic pathways. Von Passow syndrome is an association of Horner syndrome with heterochromia iridis (different colour in parts of same iris).

Sympathetic supply to the eye forms an arc of three neurons. First order neuron extend from posterolateral hypothalamus to ciliospinal center of Budge at cervical 8 to thoracic level 2 (C8-T2) in spinal cord.

Second order preganglionic pupillomotor fibers exit from thoracic level 1 (T1) and synapse in superior cervical ganglion at the cervical level 3 and 4 (C3-C4). Postganglionic vasomotor and sudomotor fibers innervate blood vessels and sweat glands of the face.

Symptoms

– Miosis or constriction of the pupil in affected eye. Dilatation of the pupil is slower after psycho sensory stimulus.

– Mild ptosis due to denervation of sympathetic nerve supply to Mϋller muscle.

– Slight elevation of the lower lid due to denervation of lower lid muscle.

– Impaired flushing and sweating ipsilaterally depending upon the site of lesion. First order neuron lesion causes anhidrosis on ipsilateral side of the body. Second order neuron lesion causes anhidrosis on ipsilateral side of face.

– Heterochromia iridis occurs in congenital Horner syndrome or in children younger than two years. Long standing Horner syndrome may also develop heterochromia.

1. Cocaine test: Topical cocaine inhibits reuptake of norepinephrine from synaptic cleft and therefore acts as indirect sympathomimetic agent. Pupil dilates poorly in Horner syndrome unlike in normal eyes. Cocaine is instilled into each eye. After 40-60 minutes, an unequal size of pupil more than 0.8 mm is significant.

2. Apraclonidine test: Topical apraclonidine has no effect on normal pupil but has mydriatic (which dilates pupil) effect on abnormal pupil. There is increased sensitivity to apraclonidine in Horner syndrome. However, in acute cases, negative apraclonidine test does not exclude Horner syndrome, where cocaine test is more helpful.

3. Hydroxyamphetamine test: Topical hydroxyamphetamine releases norepinephrine from postganglionic neurons at iris dilator muscles (which dilates the pupil). Hydroxyamphetamine in cases of Horner syndrome with intact postganglionic fiber dilates affected pupil to an equal or greater extent as compared to normal pupil. However, pupil in Horner syndrome with damaged postganglionic fiber, do not dilate as well, as the normal pupil dilates.

4. Adrenaline test: Topical adrenaline (1:1000) in preganglionic lesions, does not cause dilatation of both pupils. In postganglionic lesions, due to denervation hypersensitivity, affected pupil dilates but the normal pupil does not (with this low concentration of adrenaline).